AnodeThe negative electrode is the anode. Hydrogen is fed to it, and the hydrogen gives up its electrons here.
CathodeThe cathode is the positive electrode. Air is fed to it, and water forms here.
Electrolyte membraneIt lets hydrogen ions through and blocks electrons. Its full name is polymer electrolyte membrane, or proton exchange membrane: PEM for short.
HydrogenHydrogen gas is the fuel, fed to the anode. Each molecule is two hydrogen atoms, drawn as a pair of small circles.
OxygenOxygen comes in with air, fed to the cathode. Each molecule is two oxygen atoms, drawn as a pair of large circles.
WaterWater forms at the cathode and leaves the cell. Each molecule is one oxygen atom with two hydrogen atoms.
ElectronsElectrons cannot cross the membrane, so they travel along the wire. They go from anode to cathode.
Hydrogen ionsHydrogen ions, also called protons, cross the membrane to the cathode. Each is a hydrogen atom that has lost its electron.
Catalyst layerA thin layer of catalyst lies on each side of the membrane. It is usually platinum. On the anode side it splits hydrogen into ions and electrons.
External circuitThe wire outside the cell, here lighting a lamp. The electrons moving along it are the electric current.
How this list was compiled: Every name and fact checked on 2026-10-01, a name kept only where two independent sources use it. (1) US Department of Energy, Fuel Cells, https://www.energy.gov/eere/fuelcells/fuel-cells (a negative electrode, the anode, and a positive electrode, the cathode, sandwiched around an electrolyte; hydrogen fed to the anode and air to the cathode; a catalyst at the anode separates hydrogen into protons and electrons; the electrons go through an external circuit; the protons go through the electrolyte to the cathode, where they unite with oxygen and the electrons to produce water and heat; a fuel cell works as long as fuel is supplied), and Parts of a Fuel Cell, https://www.energy.gov/eere/fuelcells/parts-fuel-cell (the polymer electrolyte membrane, also called a proton exchange membrane, conducts only positively charged ions and blocks the electrons; a layer of platinum catalyst on both sides of the membrane; gas diffusion layers, bipolar plates and gaskets). (2) Wikipedia, text only: Proton-exchange membrane fuel cell, https://en.wikipedia.org/wiki/Proton-exchange_membrane_fuel_cell (a stream of hydrogen delivered to the anode side and split into protons and electrons; the protons pass through the polymer electrolyte membrane; the electrons travel along an external circuit; oxygen delivered to the cathode side forms water; platinum as the catalyst at both electrodes), Fuel cell, https://en.wikipedia.org/wiki/Fuel_cell (a fuel cell needs a continuous supply of fuel and oxygen, while a battery's chemicals are already inside it), and Anode, https://en.wikipedia.org/wiki/Anode (the anode is the negative electrode in a device that provides power). (3) Energy Education, University of Calgary, Fuel cell, https://energyeducation.ca/encyclopedia/Fuel_cell (hydrogen meets a platinum catalyst and splits into hydrogen ions and electrons; the hydrogen ions cross the proton exchange membrane (another name: polymer electrolyte) to the cathode and combine with oxygen to form water). Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
A hydrogen cell, or hydrogen fuel cell, makes electricity from hydrogen and the oxygen in air. Tap a part to read what it does.
Read the full guide
Hydrogen in, two paths
Hydrogen gas is fed to the anode. A platinum catalyst there splits each hydrogen molecule into hydrogen ions and electrons. The membrane lets the ions through and blocks the electrons, so the electrons go around the external circuit instead. That flow is the electric current, and here it lights a lamp.
Water out
At the cathode the ions, the electrons and oxygen from the air join to make water, with some heat. The cell keeps working for as long as hydrogen is supplied.
The quiz takes proton for hydrogen ion, PEM for the membrane and air for oxygen.
Questions and answers
How does a hydrogen fuel cell work?
Hydrogen is fed to the anode, where a catalyst splits it into hydrogen ions and electrons. The ions cross the membrane. The electrons go around an outside circuit as electric current. At the cathode both join oxygen to make water.
What are the parts of a hydrogen fuel cell?
Two electrodes, the anode and the cathode, with an electrolyte membrane between them and a layer of catalyst on each side of it. Hydrogen is fed to the anode and air to the cathode, and a circuit outside the cell joins the two electrodes.
What comes out of a hydrogen fuel cell?
Electricity, water and heat. The hydrogen ions and the electrons join oxygen at the cathode, and that makes the water.
Is the anode positive or negative in a fuel cell?
Negative. Hydrogen gives up its electrons at the anode, and they leave the cell there and flow around the circuit to the cathode, the positive electrode.
What is the difference between a fuel cell and a battery?
In a battery the chemicals that react are already inside it. A fuel cell is fed its fuel and oxygen from outside, so it keeps making electricity for as long as they are supplied.